MILAN, June 1 (Reuters) - Pope Benedict and his deputy, Cardinal Tarcisio Bertone, regarded as the chief target of a campaign of leaks, appeared side by side on Friday at the start of a visit to Milan that is unlikely to provide much respite from the scandal.

In his speech, the pontiff made no reference to the scandal, which exploded last week when his butler was arrested for stealing his private documents. Many Vatican insiders believe the butler is merely a scapegoat in a poisonous power struggle between Bertone's allies and enemies.

The pope, who has expressed sadness and pain as he faces the biggest crisis of his pontificate, greeted thousands of pilgrims in the square in front of Milan's gothic cathedral, the Duomo.

Bertone sat on a podium with the pope, the mayor of Milan and Cardinal Angelo Scola, the archbishop of Italy's financial capital.

"Let's make the pope feel our embrace. You can count on many, many friends throughout the world. Your Holiness, we love you," Scola said.

Earlier this week, Benedict renewed his trust in his "closest collaborators", which many interpreted as a gesture of support for Bertone, the Vatican's powerful secretary of state or prime minister.

The publication of embarrassing details about men Bertone has appointed or moved out and projects he has promoted or opposed suggests a concerted effort to force him out of his post.

Some 15,000 policemen have been deployed for the three-day

trip to keep protesters at bay.

The visit comes at a difficult time for the pontiff and the crisis is unlikely to be far from his mind or those of pilgrims and onlookers.

Over the past 10 days, the head of the Vatican bank was fired, the pope's butler Paolo Gabriele was arrested, and a book was published alleging cronyism and corruption in a Vatican riven by conflict between plotting cardinals.

The book reproduced leaked papal documents to back up its allegations of large-scale graft in the awarding of infrastructure projects in the world's smallest state.

Vatican police or gendarmes are scouring the city-state for more informants but they shifted focus on Friday to their more normal task of protecting the pontiff during his trips.

Their chief, shaven-headed former Italian secret service officer Domenico Giani, broke off his extremely rare criminal investigation to jog alongside the popemobile driving Benedict around Milan as his chief bodyguard.

A new aide sat in what used to be Gabriele's place on the popemobile.

PROTESTS ON TWITTER

While the pontiff might have hoped the Milan trip would give him a break from the scandal, messages posted on Twitter gave a foretaste of the sort of protests he may face in Milan.

"The pope's trip is costing 13 million euros, and all they can think about is the butler," said one.

"There are people sleeping in tents or killing themselves because they have no work. Shame on you," said another tweet, referring to thousands of people left homeless by two earthquakes over the past two weeks in northern Italy and the country's deep economic crisis.

In his speech, the pope said the victims of the earthquakes were "in our hearts and our prayers".

A recession and tough government austerity measures have hit Italy's industrial centres in the north particularly hard, with a string of suicides of businessmen in the Veneto region.

Leftist groups are organising a protest on Saturday against the "family model" promoted by the Church.

Nevertheless, trip organisers are doing their utmost to take the pope's mind off his travails.

On Friday evening he attended a concert of Beethoven's Ninth Symphony at Milan's famous La Scala opera house.

The weekend events include a meeting at Milan's San Siro stadium on Saturday with youths who recently received the sacrament of confirmation, and an open-air Mass expected to attract 1 million followers on Sunday.